Telephone-exchange apparatus.



No. 785,754. PATBNTED MAR. 28, 1905. J. L. MQQUARRIE. TELEPHONE EXCHANGEAPPARATUS.

APPLIOATION FILED MAY 27, 1901.

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UNITED STATES Patented March 28, 19u5.

PATENT ()FFICE.

JAMES L. MGQUARRIE, OF CHICAGO, ILLINOIS, ASSIGNOR TO WESTERN ELECTRICCOMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE-EXCHANGE APPARATUS.

SPECIFICATION forming part of Letters Patent No. 785,754, dated March28, 1905.

' Application filed May 27, 1901. Serial No. 62,017.

To (all 1071,0777, it nan/y concern.-

cago, in the county of Cook and State of Illinois, have invented acertain new and useful Improvement in Telephone-Exchange Apparatus, ofwhich the following is a full, clear, concise, and exact description.

This invention relates to telephone-exchange apparatus, and is concernedparticularly with what is known as overflow trunking between thediiferent sections or operators positions of a multiple switchboard.

The invention contemplates particularly a system of signals by whicheach operator is automatically informed when the traffic at the othersections of the board increases beyond a certain point.

In the operation of a telephone-exchange it frequently happens that oneoperator during the busy hour has more calls than she can attend toefliciently and quickly, while another operator at the same switchboardis not busy. Heretofore it has been customary to provide a specialsection or operators position, known as the overflow position, to whichcalls may be transferred by means of trunk-lines from sections whichhave an excess of business. This is objectionable in that itnecessitates the provision and equipment of switchboard-sections whichare in use only during acertain limited portion of each day.

The system of this invention is designed to enable an operator at anybusy position to overflow onto any other regular section or operatorsposition of the same switchboard which is not busy that is, which hasnot at the time more unanswered calls awaiting attention than a certainpredetermined number. T runk-lines between the different sections,called overflow trunks. may be used in transferring calls, and signalsare provided by which the operator who desires to transfer a call maydetermine at a glance which section is not too busy to receive it. By myinvention an operator may also be provided with a pilot-signal at herown section, which will be displayed when the traflic at her secotherless-busy sections until her work is' caught up.

My invention is illustrated in the accompanying drawing, which is adiagram showing two switchboards, or, more properly, two sections oroperators positions of a multiple switchboard connected by anoverflow-trunk and equipped with signals in accordance with myinvention.

The features or combinations which I regard as new will be pointed outin the accompanying claims.

A telephone-line is shown extending from a substation Ato an answeringspring-jack a at board A. It is understood, of course, that each linehas multiple line-jacks at all the sections of the multiple switchboard.Another line is shown extending from a substation B to a spring-jack Z)at the board or section B. We may assume that the spring-jack 7)illustrated is a line-jack.

Each line is equipped with the usual linerelay controlling asubsidiarylamp-signal, the line-relay being responsive to the flow of current whenthe circuit of the line is closed at the substation by thetelephone-switch. The several line-signal lamps at each section of theswitchboard are connected in multiple branches of a circuit includingthe common battery 0 of the switchboard. As shown in the drawing, theline-signal lamps are included in multiple grounded conductors extendingfrom the bus-bar (Z, which is connected through two relays e f inmultiple with the free pole of the battery 0. Each branch circuit iscontrolled by the line-relay of the line which the lamp in such circuitdesignates. It will be understood that all the line-signal lamps shouldbe connected to the bus-bar in this way. The relays a and f are adjustedto respond to a certain margin of current. For example, the relay 6 willrespond when three of the multiple branches containing the linesignalsare closed; but the relay f will not respond until four of the saidmultiple branches are closed. The relay 6 at each section controlssignal-circuits extending to the several other sections, thebusy-signals g in said circuits being all lighted when the relay 0 isexcited and closes the circuit. The busy-signals derive their currentdirectly from the battery 0 instead of from the bus-bar. VVhenever threecalls remain unanswered at any section, the corresponding busy-signals ywill be lighted at all the other sections to notify the other operatorsthat the section designated by the lighted'lamp is too busy to haveoverflow calls transferred to it. The relay f at each board controls thecircuit of the pilot-lamp h at the same board, so that if the unansweredcalls should reach a certain number (in this case we have assumed four)the relay f will be excited and light the pilot-lamp to inform theoperator that she should transfer some of her calls to sections whichare less busy.

A trunk-line 25, called an overflow trunk, is shown extending betweenthe boards or sections A and B. The trunk-line terminates in a plug atboard A and in a spring-jack(which may be one of the ordinaryanswering-jacks) at the other board, B. The equipment of the trunk-lineat board B is the same as the equipment of an ordinary subscriberslinethatis, there is the usual line-relay controlling-a subsidiaryline-signal lamp and a cut-off relay for disconnecting the line-signalapparatus, the cut-off relay being in the usual local circuit, which isclosed in registering contacts of the answering-plug and the spring-jackwhen the jack is plugged into in answering aeall. The spring-jack of theoverflow trunk-line is designated by the letter a. At the board A thebusy-signal g, which corresponds to the board B, is preferably locatednear the plug 6, which forms the terminal of the overflow trunk-lineextending to board B. The plug 2? is shown to be an ordinary three-partplug, the tip and ring contacts which form the terminals of the limbs l2 of the trunk-line being adapted to engage the short and long linesprings, respectively, of any spring-jack into which it is inserted. Atthe board B the short and long line springs of the jack a are connectedwith the limbs 1 2, respectively, of the trunk-line. The effect ofinserting the plug 6 into a spring-jack at board A, then, is simply toextend the line thus plugged into to the springjack (0 at board B, theline-signal apparatus connected with said spring-jack a beingautomatically operated in the same manner as the regular line-signalapparatus of the callingline was operated in the lirstinstance. When acall is extended in this way, the connection will be supervised by theoperator who answers it-that is, assuming a call to be transferred fromA to B, the operator B would supervise the connection, the work requiredof her being no different from that required in answering any ordinarycall. The jacks of the overflow trunks may be among the ordinaryanswering-jacks at her section.

At the board which transfers the call a disconnect-lamp 2' may beprovided for the trunkline, this lamp being lighted when the connectionis taken down at the board which answers the call. The circuits fordisplaying this disconnect -lamp are illustrated in the drawing, butsince they form no part of the present invention will not beparticularly described.

Supposing that subscriber A desires a connection with subscriber B, heremoves his telephone from its hook, thus closing the linecircuit andbringing about the illumination of the line-signal lamp 7r. Ordinarilythe operator at the section A would answer the call in the usual mannerand the connection would be completed by inserting one plug of a pair inthe jack of the calling-line and the other plug in the multiple jack ofthe line called for. If, however, she had four calls at that timeunanswered and awaiting attentionthat is, if four line-signal lamps 7::were lightedthe relay 7' would be excited and her pilotsignal itdisplayed. She would know from the illumination of this signal that shewas at liberty to transfer the call to some other section, and she wouldtherefore simply pick up one of the trunk-plugs 25 whose correspondinglamp 9 was not lighted and insert it into the answering-jack of thecalling-line, thus extending the connection to the trunkjack (4 at thedistant board. The busy-lamp associated with each trunk-plug, serves toinform the operator of the condition of the board to which thattrunk-line extends.

If in the case we have assumed three linelamps were lighted at thesection B, the relay 6 at that section would be excited and the circuit3 of the busy-lamp g closed, causing the display of the signal. Theoperator at board A, who was about to transfer a call, would thereforenot use the trunk-plug t, since she would know by the lighting of thelamp 1 corresponding to said plug that the distant board was already toobusy to accommodate overflow calls.

Having thus described my invention, I claim as new, and desire to secureby Letters Patent, the following:

1. The combination with the several sections of a switchboard, ofoverflow trunk-lines between the sections, busy-signals for each sectionat the other sections, and magneticallyactuated apparatus at eachsection for controlling the busy-signals thereof at the other sections,whereby each operator is automatically informed which of the othersections is at liberty to receive overflow calls.

2. The combination with two sections of a switchboard, of line-signalsfor the telephonelines at one of said sections, a busy-signal at thedistant section, and means controlled by the joint operation of apredetermined number of said line-signals, for controlling saidbusy-signal, wherebythe busy-signal is displayed at the distant sectionwhen av given number of calls are received.

3. The combination with two switchboards and telephone-lines centeringat each board, of line-signals for the telephone-lines, connectingappliances at each board for answering calls, a trunk-line between theboards, a busysignal for one board located at the other board, and meanscontrolled by the joint operation of a predetermined number ofline-signals at the board to which the busy-signal corresponds, forcausing the display of said signal, whereby the operator at the boardWhere the busy-signal is located is informed whether or not calls may betrunked to the distant board.

4:. The combination with several telephonelines, of switches for saidlines operated from the substations of the lines, circuits controlled bythe switches, a device responsive only to current existingsimultaneously in several of said circuits, and mechanism controlled bysaid device.

5. The combination with two switchboards and telephone-lines havingmultiple connections on both boards, connecting appliances at each boardfor answering calls, an overflow trunk line between the boards, meansfor transmitting call-signals from the substations of the lines,responsive devices, one for each line at one of the switchboards,adapted to be set by a call-signal transmitted from the substation ofsuch line, means actuated in answering a call, for restoring saidresponsive devices, and a signal at the distant board controlled by thejoint actuation ol a predetermined number of said responsive devices.

6. The combination with a switchboard and telephone-lines centeringtherein, of a source of current, a circuit for the same, multiplebranches for said circuit, line-signals for the telephone lines in theseveral multiple branches, switches controlling said multiple branches,a magnet included serially in the circuit with all the multiple branchesand adjusted to respond when a predetermined number of said branches areclosed, and a signal controlled by said magnet, substantially asdescribed. v

7. The combination with a switchboard and telephone-lines centeringtherein, signals for the lines, a source of current, and a circuittherefor adapted to be completed in switchcontacts controlling saidsignals, of a relay included in said. circuit responsive to the jointoperation of a predetermined number of said signals, and mechanismcontrolled by said relay, substantially as described.

In witness whereof I hereunto subscribe my name this 18th day of April,A. D. 1901.

JAMES L. MGQUARRIE.

WVitnesses:

ELLA EDLER, EDWIN H. SMYTHE.

